镁处理对船板钢中钉扎粒子的作用机制  

Mechanism of Mg treatment on pinning particles for shipbuilding steel

作　　者：李慧蓉 孙立根 张鑫 王博 张彩军 朱立光 LI Huirong;SUN Ligen;ZHANG Xin;WANG Bo;ZHANG Caijun;ZHU Liguang(College of Electrical Engineering,North China University of Science and Technology,Tangshan 063210,Hebei,China;College of Metallurgy and Energy,North China University of Science and Technology,Tangshan 063210,Hebei,China;Department of Development Planning and Discipline Construction,North China University of Science and Technology,Tangshan 063210,Hebei,China;Hebei University of Science and Technology,Shijiazhuang 050018,Hebei,China)

机构地区：[1]华北理工大学电气工程学院,河北唐山063210 [2]华北理工大学冶金与能源学院,河北唐山063210 [3]华北理工大学发展规划与学科建设处,河北唐山063210 [4]河北科技大学,河北石家庄050018

出　　处：《钢铁》2024年第8期138-150,共13页Iron and Steel

基　　金：中央支持地方资助项目(236Z1015G);河北省钢铁联合基金资助项目(E2021209083,E2021209022);河北省创新能力提升计划资助项目(23561006D)。

摘　　要：镁处理可以大幅提高船板钢的大线能量焊接性。钢中加入镁一方面可以实现夹杂物的细化,提高了夹杂物对IAF诱发的概率;另一方面镁可以增强钢中第二相粒子的高温稳定性,有效抑制了大线能量输入下HAZ原奥氏体晶粒的粗化。其中钢中第二相粒子稳定的钉扎作用是镁氧化物冶金作用实现的关键,但相关领域的研究,特别是镁对钉扎粒子的影响机制还有待进一步深入。为此从不同焊接线能量的热模拟试验出发,系统分析了焊接线能量对钉扎粒子构成的影响,并结合粒子析出和MgO生成热力学、化合物晶体学关系和钢中元素的扩散行为等进行分析和讨论,以期确定镁对钢中钉扎粒子的影响机制。研究结果表明,对于镁处理船体钢,当焊接线能量超过200 k J/cm时,钢中的钉扎粒子会出现部分解钉失效的现象。而随着焊接线能量的增大,HAZ中的钉扎粒子尺寸经历了先减小后增大的变化过程,并且焊接线能量越大,大尺寸的TiN粒子越多。此时的钉扎粒子多为以TiN-MgO-Al_(2)O_(3)为基体、表层附着部分含Nb C的复合粒子。粒子析出热力学、MgO生成热力学、粒子析出错配度关系和钢中元素扩散系数分析结果表明,由于MgO生成和TiN析出的温度区间较为接近,且两者为共格析出,在长时间的高温作用下会生成MgO-TiN复合析出物,使钢中第二相粒子的高温稳定性大幅增强。基于焊接热模拟试验和理论分析结果可以看出,钢液经过镁处理后,在连铸和大线能量焊接过程中均有可能生成高温稳定的MgO-TiN-Al_(2)O_(3)复合粒子。但对于试验钢,钢中MgO的量远低于TiN析出量,TiN的溶解势必会影响钢中第二相粒子的钉扎效果,因此,提高钢中镁含量是提高镁处理船体钢大线能量焊接性的关键。The capacity of shipbuilding steel for large heat input welding could be significantly improved by Mg treatment.On the one hand,the addition of Mg in steel could refine the inclusions and improve the probability of IAF inducing.On the other hand,Mg could enhance the high-temperature stability of pinning particles,and effectively restrain the coarsening of original austenite grains in HAZ.The high-temperature stability of second phase particles in steel is the key to the effect of Mg oxidation metallurgical,but further in-depth research is still insufficient,especially the influence mechanism of Mg on pinning particles.Therefore,this study starts from the welding simulation experiments of different welding heat input,systematically analyzes the influence of heat input on the constitution of pinning particles in steel,and analyzes and discusses based on the thermodynamics of particle precipitation,thermodynamics of MgO generation,crystallography relationship between particles,and diffusion behavior of elements in steel.The purpose is to ascertain the influence mechanism of Mg on pinning particles in steel.The results show that,for the industrial shipbuilding steel with Mg treatment,when the welding heat input exceeds 200 kJ/cm,some pinning particles will lose their effectiveness.With the increase of welding heat input,the size of pinning particles in HAZ first decreases and then increases,and the more large-sized TiN particles with higher welding heat input.At this time,most pinning particles are composite particles,with TiN-MgO-Al_(2)O_(3)as the matrix,coated with NbC particles on the surface.The results of particle precipitation thermodynamics analysis,MgO generation thermodynamics analysis,particle precipitation mismatch relationship and diffusion coefficient analysis of elements in steel show that,due to the close temperature range of MgO generation and TiN precipitation,and their co-precipitation behavior,MgO-TiN composite precipitates will generate with long-term high temperature,and greatly enhance the high-

关 键 词：镁处理 钉扎粒子 大线能量焊接 船体钢 氧化物冶金 

分 类 号：TG142.1[一般工业技术—材料科学与工程]